From a7303360aea203d0f58f77ac43287f5b98c7cbe6 Mon Sep 17 00:00:00 2001
From: Dmitri Gribenko <gribozavr@gmail.com>
Date: Wed, 9 Jan 2013 15:25:30 +0000
Subject: [PATCH] Configure: if we compile with clang, check that it is not
 broken

Some linux distibutions (for example, Mageia 2, Fedora 17) ship Clang that is
essentially broken for the end user.  Clang can not find or compile libstdc++
headers.

The issue is that our configure prefers clang over gcc, thus selecting a broken
Clang when a working GCC is available.

Now we detect this issue by compiling a simple program.  If it does not
compile, configure stops with an error suggesting the user to select a
different compiler.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171975 91177308-0d34-0410-b5e6-96231b3b80d8
---
 autoconf/configure.ac | 26 ++++++++++++
 configure             | 95 ++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 119 insertions(+), 2 deletions(-)

diff --git a/autoconf/configure.ac b/autoconf/configure.ac
index 102147c4f2c..a1426c1832d 100644
--- a/autoconf/configure.ac
+++ b/autoconf/configure.ac
@@ -65,6 +65,32 @@ AC_PROG_CC(clang llvm-gcc gcc)
 AC_PROG_CXX(clang++ llvm-g++ g++)
 AC_PROG_CPP
 
+dnl If CXX is Clang, check that it can find and parse C++ standard library
+dnl headers.
+if test "$CXX" = "clang++" ; then
+  AC_MSG_CHECKING([whether clang works])
+  AC_LANG_PUSH([C++])
+  dnl Note that space between 'include' and '(' is required.  There's a broken
+  dnl regex in aclocal that otherwise will think that we call m4's include
+  dnl builtin.
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <limits>
+#if __has_include (<cxxabi.h>)
+#include <cxxabi.h>
+#endif
+#if __has_include (<unwind.h>)
+#include <unwind.h>
+#endif
+]])],
+[
+  AC_MSG_RESULT([yes])
+],
+[
+  AC_MSG_RESULT([no])
+  AC_MSG_ERROR([Selected compiler could not find or parse C++ standard library headers.  Rerun with CC=c-compiler CXX=c++-compiler ./configure ...])
+])
+  AC_LANG_POP([C++])
+fi
+
 dnl Configure all of the projects present in our source tree. While we could
 dnl just AC_CONFIG_SUBDIRS on the set of directories in projects that have a
 dnl configure script, that usage of the AC_CONFIG_SUBDIRS macro is deprecated.
diff --git a/configure b/configure
index 4392e976ae5..3ca2df90abf 100755
--- a/configure
+++ b/configure
@@ -3471,6 +3471,98 @@ ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $
 ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
+if test "$CXX" = "clang++" ; then
+  { echo "$as_me:$LINENO: checking whether clang works" >&5
+echo $ECHO_N "checking whether clang works... $ECHO_C" >&6; }
+  ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <limits>
+#if __has_include (<cxxabi.h>)
+#include <cxxabi.h>
+#endif
+#if __has_include (<unwind.h>)
+#include <unwind.h>
+#endif
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext
+if { (ac_try="$ac_compile"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_compile") 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_cxx_werror_flag" || test ! -s conftest.err'
+  { (case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_try") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_try") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+
+  { echo "$as_me:$LINENO: result: yes" >&5
+echo "${ECHO_T}yes" >&6; }
+
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+
+  { echo "$as_me:$LINENO: result: no" >&5
+echo "${ECHO_T}no" >&6; }
+  { { echo "$as_me:$LINENO: error: Selected compiler could not find or parse C++ standard library headers.  Rerun with CC=c-compiler CXX=c++-compiler ./configure ..." >&5
+echo "$as_me: error: Selected compiler could not find or parse C++ standard library headers.  Rerun with CC=c-compiler CXX=c++-compiler ./configure ..." >&2;}
+   { (exit 1); exit 1; }; }
+
+fi
+
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+fi
+
 
 
 if test -d ${srcdir}/projects/llvm-gcc ; then
@@ -10393,7 +10485,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<EOF
-#line 10396 "configure"
+#line 10488 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -16330,7 +16422,6 @@ rm -f core conftest.err conftest.$ac_objext \
 
 
 
-
   { echo "$as_me:$LINENO: checking for HUGE_VAL sanity" >&5
 echo $ECHO_N "checking for HUGE_VAL sanity... $ECHO_C" >&6; }
 if test "${ac_cv_huge_val_sanity+set}" = set; then
-- 
2.34.1